Floating roof



Feb. 16, 1954 M. K. ALLEN ETAL FLOATING ROOF 2 Sheets-Sheet l Filed Jan.21. 1953 M. K. ALLEN ETAL Feb. 16, 1954 FLOATING ROM1 2 sheets-sheet 2Filed Jan. 2l, 1955 Patented Feb. 16, 1954 attain UNITED STATES PATENTOFFICE flankl Mfg. '"Co.,`lnc., East Chicago, Ind., a

corporation of Delaware Application January 21, 1953, Serial No.332,4'77

4 Claims. l This invention relates to the sealing and centeringmechanism of a oatng roof for the I` r0- tection of gasolineand thelike. It is known that sealing means must be applied to the peripheralspace around a oating roof in order to avoid vapor losses and that theroof must be kept substantially centered against windpressu're and thelike in order to avoid `injury to the Vseal and other parts of theinstallation. Itis also known 'to app-ly both sealing and roofcenteringv yiorces by a series of suitable levers. Each of these leversusually has one end pivoted to the iloating roof, the opposite endweighted below the floating roof, land an intermediate por tion actingupon the seal, either directly like a crowbar or indirectly throughadditional linkage which may also serve to support the weight oftheseal.

According to the present invention the intermediate portion of such alever acting like a crowbar is curved to provide a seal contacting, loadabsorbing cam or rocker surface in order to produce ra variable loadarm. More particularly the cam varies the load arm so that as thefloating roof approaches the seal, a more than propor- "il tionally`increased net force is derived from the 'uniform weight attached to thelever. In this manner the new weight and Vlever system produces sealingand centering effects which are superior to thoseobtainable from theearlier weighted levers and also superior to those of the resilientspring pushers, known `to the art. The construe tion `and maintenancecost of the new device is at most equal to that of the earlier weightedlevers and considerably less than that of the earlier spring pushers.

These and `other features of the new mechanism will be understood moreclearly from the description of preferred embodiments which follows.

In the drawing:

Figure 1 is a partial cross-sectional view of a floating roof utilizingthe present invention.

Figure 2 s a similar view of another part of the same floating roof.

Figure 3 is a graph of forces utilized in vthe new mechanism.

Figure 4 is a diagrammatic plan View of a floating roof using the newmechanism.

Figure 5 is a free-body diagram o1' a hanger lever from Figure 2,showing `some of the forces summarized .in Figure 3.

Figure 6 is a similar diagram of a. pusher lever from Figure 1., showingAadditional forces summarized in Figure 3.

Figure 7 isa view generally similar vto Figures (Cl. 2ML-26) 2 l 'and 2but showing modified `pusher and hanger levers.

`Referring rst to Figures 1 to 6:

The floating roof comprisinga deck D and rim R, noa'ts von .a volatileliquid such as gasp- .line "G, stored in Athe 'tank T. The `deck Dcovers the liquid surface L except a narrow, annular; peripheral spaceP. The clearance 'provided by this space allows slightly irregular,basically ecolill " nomical construction of vthe tank T and roof F.

In order to avoid vapor loss the space VP is covered by a exible seal Sformed by 'an annular strip of rubberized fabric vor the like, Vtheinner edge of which is secured to the top of the rim R. The outer edgeof this -seal S is attached to the upper edge of a seal `shoe SScontacting the inside of the tank T and forming an annular ring of thinmetallic material such as lli-gauge steel.

`n series of rigid pusher levers l0 are pivoted to and peripherallyspaced around the rim R ot the floating roof F, desirably `at peripheraldis*- tanc'es such as about 3 to dit. from one another, Each pusherlever preferably consists in an elona gated steel bar rolled into acontinuous, circuslar. outwardly convex arc. It has an upper end portionconnected with the oating roof rim R `by a pivot pin H: such pin beingtransversely welded to the bar lil and ypivoted in a pair of pivot clips`I IA welded to the rim R. The at tachxnent and orientation of the pivotclips l IA is such that the kpusher I6 swingable in a subfstantiallyvertical plane, `substantially Aradial of the oating roof.. A weight l2is secured to the `free end portion of each pusher l0, below the deck Dand inwardly of the rim R. Throughout its length between the pivot H andweight AI2 each bar I0 lhas an outwardly convex, preferably arcuate camor rocker surface IUC, which contacts the seal shoe SS at a point X, theposition of which depends on the local width of the space P. The bar l0contacts the vseal shoe SS with outward pressure, due to the weight l2which tends to pry the floating roof away from the tank shell.

The arcuate pushers are formed veryI simply by cold rolling plain barsof predetermined length to a predetermined radius. vAn arc of aboutA'ldegrees with 'a radius of about twenty-four inches is preferred When itis desired to keep the width `of the space P within a range 'of aboutthree to ten inches. l

The cold rolling operation mentioned is simpler andsafer than its theformation 'of a sharp bend of predetermined llocation `and aneularty asused in some of the earlier pusher levers. Likewise the new pusher leverI is of extreme simplicity, economy and reliability as a moving element,being equipped only with a single pivot |l.

Hanger arms or support links are provided in addition to the pushers Il)in order to support the Weight of the seal assembly S, SS. Theseadditional links or levers are spaced around the floating roof atperipheral distances such as about 3 to 6 ft. from one another, suitablyinterspersed with the pushers l0. As shown in Figure 2 each hangerextends from an inner, lower pivot 2|, suitably secured to the floatingroof F, through the space P to an outer, upper pivot 22, secured to thesteel shoe SS. Preferably each being slidable in an upstanding guidesleeve inner, lower pivot 2| is formed in a clip 23 secured to a slidemember V24; the slide member secured to the underside of the deck D by agusset 26. A compression spring- 21 surrounding the slide 24 bearsagainst the top end of the sleeve 25 and the underside of the clip 23,in order to make the support of the seal shoe vertically resilient andthereby to avoid deformation of the shoe and partial loss of sealingefficiency incident to the required pivoting movements of the hangerlink 20.

In order to minimize interference of the parts l0, 25 with a closeapproach of the floating roof F to the tank wall T, whenever such anapproach is required, it may be desirable to cut notches I3'into theoutermost edge portion of the deck D, outside the rim R, at positions inregister with said parts I0, 25.

The sleeve 25 may be installed in an upright but slightly inclinedposition as shown in order 'to minimize the side thrust which tends tooccur due to the eccentric column loading of the hangers 20. However,this inclined arrangement is subject to modification. In fact it issometimes possible to omit the entire resilient slide mechanism. VInthat event, as shown in Figure 7, the

hangers 40 can be plain, rigid bars, interconnecting pivots which arerigid with the floating roof F and seal shoe SS.

Figure 7 is also modied as to the pusher 30 which in this case comprisesan upper, outwardly curved portion 3|, extending from adjacent the rim Rto and slightly beyond the seal shoe SS; an intermediate elbow 32; and alower, straight, more or less horizontal portion 33, extending from thiselbow to the region below the deck end Within the rim, where saidportion is suitably weighted. This modified pusher design is suitablemainly when the radius of curvature in the'upper or cam portion 3| isrelatively long; and this again may be desirable in order to apply theVsealing pressure in predetermined regions of the seal.v However, apusher lever forming an unbroken, short radius arc, as used in Figure l,is very satisfactory in most cases; certainly more so than is theapplication of pressure with a fixed load arm as used up to now.

This latter point will become clearer from a description of theoperation of the preferred device which follows:

Referring to Figure 4, the action of wind W tends to uncenter thefloating roof relative to the tank. This tends to interfere with themost eflicient arrangement ofthe seal S. It also tends to loosen drainpipes DR and to jeopardize other parts. Therefore uncentering must Vbecounteracted and mainly the seal action maintained.

The maintenance of seal actionis eiected, to

liii

some extent, by the hangers 20 alone, but these hangers tend to uncenterrather than center the floating roof. Due to its outwardly inclinedposition, and the weight of the parts 20, S, SS, each hanger 20 appliesby the upper pivot 22, an outward pressure P20 to the seal SS, with anin- Ward pressure reaction, applied to the hanger itself (see Fig. 5).An inward pressure reaction R20, equal in magnitude to the outwardpressure P20, is applied to the floating roof by the inner pivot 2|.These pressures P20, R20 increase, about proportionally, with increasingdistance between the floating roof and the tank shell. However, for thepurpose of centering the floatingroof they would have to increase as thedistances are reduced.

In order to make this last point quite clear, reference should be had toFigure 4 again. When the wind, acting in direction W, urges the floatingroof F toward the hangers 20| at one side of the tank', these hangersturn into more upright positions, causing local reduction ofV pressuresP20, R20. The opposite hangers 20-2 cause the opposite effect by turninginto more inclined positions. Therefore, as soon as the wind has movedthe oating rcof in direction W beyond the centered position the pressurereactions R20 of the hangers 20| are less than those of the hangers20-2. Thus the hangers actually aid the wind pressure in uncentering thefloating roof.

These uncentering effects are most eiciently and economicallycounteracted by the new pushers |0. When the floating roof is uncenteredas described, this causes certain shifts in the positions of thesepushers. Referring again to Figure 4, the pushers |0| adjacent thehangers 20-| have their weights raised and their contact points Xbrought closer to their pivots. At the same time the opposite pushersIll-2 have their weights lowered and their contact points X broughtfurther away from their pivot.

The raising and lowering of the Weights, which is known to the art, hasa useful Veiect in counteracting the uncentering forces. This effecthowever, is at most approximately proportional to the lateraldisplacement of the floating rool,l

since it is. derived from a mere increase of the Weight arm A-l2 of aswinging pusher lever. In the present mechanism this effect is greatlyaugmented, since the load arm AP of each pusher lever is reduced whileits weight arm A|2 is extended, and vice versa. In this manner theincrease in the pressure reaction R|0, produced by each pusher |0 can bemade more than proplortlional to the degree of approach to the tank s eBy varying the profile of the cam |0C the load arms AP can be varied indifferent, predetermined manners. In practice, the circularly arcuatecam profile is most simply produced; and this profile has ample effectfor the purpose of counteracting the uncentering forces with efliciencyand safety (even in the event thatV some pushers become frozen orotherwise inoperable upon prolonged use). l

It may be well to point out at this point that, when the floating roofmoves horizontally, shifting the weight arm A|2 and load arm AP, somesliding friction may take place between the cam surface |0C and thesealSS, depending on the type of hanger 20 or 40 that is used. Astarting friction SF, acting either upwards or downwards (depending uponthe direction of the floating roofs motion), may have to be overcomebefore the position of the pusher lever |0 is actually changed. Inpractice this involves no very sericus problem. The pusher lever Iii cancontact the seal SS with a relatively wide surface, there bydistributing the frictional load adequately.

A summary of the essential pressure reactions obtained by the levers i0and 2E! is shown in Figure 3, for a typical floating roof embodying thepresent invention.

The curve R29 shows the pressure reactions of the same designation whichare caused by the hangers and the weights supported thereby (Fig. 5).The curve RIU shows the pressure reactions of the same designation whichare caused by the pushers i0 due to their aforementioned changes ofweight and load arms; consideration being given also to incidentalmatters such as variations in the distribution of weight of the pusherlever itself. The curve RT shows the sum of R-I 0 and R-2il. It isassumed that the floating roof is centered at the distance of six and ahalf inches from the tank shell. As shown by the graph, the pressuresR-T of all pusher-hanger combinations, when the roof is so centered, areslightly more than 30 lbs. Assuming now that the floating roof is driventoward one side by wind pressure and that accordingly the width of thespace P on that side is reduced to three and a half inches, adjacent thehangers and pushers IIJ-I, '2U-4, the width of the space is accordinglyincreased to about nine and a half inches adjacent the opposite pushersand hangers ill-2, 2li-2. At the first mentioned points the floatingroof is exposed to inwardly acting forces RIU plus R20, the sum of whichas shown by the curve RT is in excess of lbs., that is, sharplyincreased. At the corresponding opposite point the curve RT shows aninward, opposite pressure of less than 25 lbs., that is, less than thepressures in centered position and only slightly more than the minimumpressures shown. Thus there exists a centering force in excess of 25lbs. for the rst mentioned points. This force is multiplied by thenumber of linkage elements eiectively lying in the line of action of thewind pressure; and this number.

again, depends upon the size of the tank, as does the effect of the windpressure itself. The more than proportional outward increase of thepusher pressure is reflected by the pronounced downwardly convexity ofthe curve RID and the similar form of the curve RT.

As a result of this new and advantageous arragement of pressureconditions the total amount of Weights I2, required with a given seal S,SS and hanger system 20, is considerably less than in earlier designs.This feature reduces the cost of the mechanism, directly and indirectly.

This is a continuation in part of the copending applications S. N.149,956, led by the undersigned, on March 15, 1950, now abandoned, S. N.200,713, filed on December 14, 1950, by Reign C. Ulm, now abandoned. Thefirst copending appits-ation showed a pusher lever similar to that ofthe present Figure 7. The second copending application showed a pusherlever similar to that of the present Figure 1. The hanger arms shown inboth copending cases were similar to those of the present Figure 7.

We claim:

1. A floating roof comprising in combination with peripheral rim and aseal ring supported therefrom, a series of rigid pushers distributedaround the rim, each pusher' having an upper end portieri forming apivot and connected with the rim for swinging motion in a substantiallyvertical plane substantially radial of the floating roof, a weightedlower end below the floating roof, inwardly cf the pivot, and anintermediate cam and rocker portion extending from adjacent the pivot atleast over a major portion of the pusher toward the weighted end, withpronounced, arcuate, Outward, substantially uniform curvature in theouter surface of the entire cam and rocker portion, with steep downwardand outward extension in the cam and rocker portion adjacent the pivotand with progressively steep downward and outward extension to a pointof tangential contact between the cam and rocker portion and the sealring, so that the 1ocation of the said point of contact is verticallyvariable to a substantial extent as compared with the displacement ofthe weighted end of the pusher, in response to horizontal movements ofthe oating roof relative to the seal ring.

2. A fioating roof as described in claim 1 wherein said curvature insaid outer surface of the cam and rocker portion is circular.

3. A floating roof as described in claim 2 wherein the circularcurvature extends throughout the entire extension of the pusher from thepivot to the weighted end.

4. A floating roof as described in claim 3 wherein the outer surface ofthe cam and rocker portion of each pusher forms an arc of about MARVINK. ALLEN. REIGN C. ULM.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,660,021 Wiggins Feb. 21, 1928 1,903,306 Williams Apr. 4,1933 1,986,869 Welp Jan. 8, 1935 2,554,497 Moyer May 29, 1951

